Connector lead for electrical apparatus and combination thereof with said apparatus

ABSTRACT

In combination with an electrical apparatus having an aluminum sheet winding, a multiple layer strip-type connector lead between the winding and a terminal spaced from the winding, and a method of making said connector lead. One end of the connector lead is mechanically and electrically secured to a convolution of the aluminum sheet winding by one or more pluglike welds, the connector lead being secured at the opposite end thereof to a terminal stud or studs. When the connector lead is of aluminum, it may be plated with tin or other suitable metal on at least the end thereof connected to the terminal stud or studs to prevent formation of an aluminum oxide coating on the portion of the connector lead which is so plated.

United States Patent [72] Inventors Ralph D. Wakeam Gadsden, Ala.; Edward Soref, Milwaukee, Wis.

[21] App1.No. 859,932

[22] Filed Sept. 22, 1969 [45] Patented Nov. 2, 1971 [73] Assignee Allis-Chalmers Manufacturing Company Milwaukee, Wis.

[54] CONNECTOR LEAD FOR ELECTRICAL APPARATUS AND COMBINATION THEREOF WITH SAID APPARATUS 23 Claims, 4 Drawing Figs.

[52] U.S. C1 336/192,

[51] Int. Cl 1-10lj 15/10 [50] Field of Search 336/192,

[56] References Cited UNITED STATES PATENTS 1,303,964 5/1919 Rietzel 336/192 X 1,405,534 2/1 922 Merritt 174/1262 X Primary Examiner-E. A. Goldberg Att0meys- Robert C. Sullivan, Robert B. Benson and Lee H.

Kaiser ABSTRACT: In combination with an electrical apparatus having an aluminum sheet winding, a multiple layer strip-type connector lead between the winding and a terminal spaced from the winding, and a method of making said connector lead. One end of the connector lead is mechanically and electrically secured to a convolution of the aluminum sheet winding by one or more pluglike welds, the connector lead being secured at the opposite end thereof to a terminal stud or studs.- When the connector lead is of aluminum, it may be plated with tin or other suitable metal on at least the end thereof connected to the terminal stud or studs to prevent formation of an aluminum oxide coating on the portion of the connector lead which is so plated.

CONNECTOR LEAD FOR ELECTRICAL APPARATUS AND COMBINATION THEREOF WITH SAIDAPPARATUS BACKGROUND OF THE INVENTION 1.'Field of the Invention v This invention relates to electrical apparatus such. as stationary electrical inductionapparatus or the, like, and more particularly to the connection of conductive leads, such as tap leads or the like, to the winding of an electricalapparatus.

This invention will be described as embodied in a voltage regulator of the step type and to the tapleads therefor, but it will be understood that the invention is applicable to other types of electrical apparatus, and particularly to other types of stationaryelectrical induction apparatus and to the connec tion leads therefor.

2. Description of the Prior Art In the construction of tap leads for electrical induction apparatus such as step-type voltage regulators, in order to satisfy the current-carrying and flexibility requirements for the. tap lead it is common practice to use multiple layer tap leads. In the past, such multiple layer tap leads have commonly been made of copper.

When the inductive winding is made of aluminum sheet rather than of copper magnet wire, it is preferable. to use tap leads formed of aluminum strip. Aluminum strip tap leads are lighter in weight and lower, in cost then copper tap leads. Aluminum strip tap leads are also easily hot welded to the amminum sheet by the electric are spot weld process. The aluminum strip tap leads may be joined by coldwelding to the aluminum sheet. However, the use of coldwelding does not permit the simultaneous welding of as many tap lead layers of aluminum strip of a given thickness as does the use of a hot welding process such as the arc spot metal are process described, for example, in U.S. Pat. No. 3,102,948-McCampbell et al.

Because hot welding permits the attachment of a greater number of aluminum striplead layers of a given thicknessto the aluminum sheet winding than is possible with cold welding techniques, aluminum strip tap leads having a higher range of current-carrying capacities can be attached to the aluminum sheet winding by the hot-welding method than by the coldwelding method.

A further advantage of the use of a hot weld to join the aluminum tap lead to the aluminum sheet winding is that the removal of the aluminum oxide layer from the aluminum sheet and from the aluminum tap lead by wire brushing, grinding, or other mechanical means is not required in order to obtain a reliable mechanical joint between the sheet winding and the tap lead with satisfactory conductivity.

When used in a tap changing type of electrical induction apparatus, such as a step-type voltage regulator, tap leads formed of bare aluminum conductors do not have a low enough contact resistance when bolted to tap changer studs because of the high-resistance aluminum oxide layer on the aluminum, and the relatively small surface contact area of the bolted connection, and even wire brushing prior to bolting does not lower the connection resistance sufficiently to satisfy the requirements for this application.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved connector lead suitable for connection to an aluminum-sheet-type winding in an electrical apparatus.

It is another object of the invention to provide an improved multiple layer aluminum tap lead construction and connection foruse with an aluminum sheet winding in an electrical apparatus, such as an electrical induction apparatus. C It is another object of the invention to provide an improved connector lead or tap lead for connection at one end thereof to an aluminum-sheet-type inductive winding or the like and at the opposite end thereof to a terminal for the tap lead or the like.

Still another, object of the invention is to provide a connector lead such asa tap lead or the like for use with an electrical winding or the like, which connector lead has low-contact resistance characteristics atthe electrical connections at both ends thereof.

Still another object of the invention is to provide a tap lead connection for an electrical apparatus such as a stationary electrical induction apparatus or the like having an improved electrical and mechanical connection to the winding of. the electrical apparatus.

StiILanotherobject of the invention is to provide in combination with an. aluminumrsheet-type winding for an electrical apparatus a connector having improved electrical and mechanicalconnections tothe winding.

Still a further object of the invention is to provide in combination, with an electricalapparatus having an. aluminum sheet winding a connector leadhavingimproved electrical and mechanical cha acteristics.

In achievement of these objectives,.there is provided in accordance with this invention in combination with an electrical apparatushaving an aluminum sheet winding a multiple layer strip type connector lead between the winding and a terminal spaced from the winding. One end of the connector lead is mechanically and electrically secured to a convolution of the sheet winding by one or more pluglike welds, the connector lead being secured at. the opposite end thereof to a terminal stud or studs. When the connector lead is of aluminum, it may be plated with tin or other suitable metal on at least the end thereof connected to the terminal stud or studs to prevent forportion of the BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in elevation, partially broken away, of a steptype voltage regulator embodying tap leads in accordance with the invention;

FIG. 2 is a view in vertical elevation of a tap lead in accordance with the. invention connected at one end to an aluminum-sheet-type winding of a steptype voltage regulator or the like and at the opposite end to the terminal board for the voltage regulator or the like;

FIG. 3 is a side elevation view ofthe tap lead and connections therefor of FIG. 2; and

FIG. 4 is a schematic wiring diagram of a step-type voltage regulator which may incorporate tap leads and connections therefore as shown in FIGS. 1, 2 and 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing there is shown a tank generally indicated at 10 in which is positioned a step voltage regulator generally indicated at 12 including an exciting winding 14 adapted to be connected across a circuit to be regulated and a series winding 16 adapted to be connected in series with the circuit to be regulated. The windings l4 and 16 are inductively related to each other by means of a magnetic core 18. As is well known, the voltage of the circuit 20 is varied in steps by operation of a load tap changing mechanism, including a revet'sing switch assembly 22 which effects variations in voltageeither below or above the voltage supplied to the exciting winding 14. The series winding I6 is provided with a series of taps 25 connected by tap leads 26 to stationary contacts 28. Zero tap contact 28' is connected to terminal 30 of the regulator. The stationary contacts 28 and 28 are mounted in circumferentially spaced relation to each other on a stationary panel 32 (FIG. 1), and form part of a dial-type tap changing switch 27. The tap changing switch 27 also comprises a pairof movable contacts 340 and 341) which are connected to the circuit 20 through a midtap reactor 36. The movable contacts 34 and 34b are affixed to a shaft, not shown, and are circumferentially spaced apart so that by rotation of the shaft both movable contacts 340 and 34b may be disposed on one stationary contact 28 or 28' or in bridging relation with respect to adjacent stationary contacts. For a detailed description of a typical step voltage regulator employing a circuit of the type shown in FIG. 4, and incorporating a tap winding such as the tap winding 16, reference is made to U.S. Pat. No. 2,947,838, to Benon F. Ureda, issued Aug. 2, 1960.

AS best seen in FIGS. 1, 2 and 3, the winding 16 is shown as being formed of a convolutely would aluminum sheet 38 having tap leads 26 connected to predetermined spaced turns of the winding 16. Winding I6 is provided with suitable turn-totum electrical insulation, not shown in the drawing. The aluminum sheet 38 may typically be about 0.006 inch (6 mils) thick. As best seen in FIGS. 2 and 3, each tap lead 26 is formed of a spirally wound strip of aluminum. In a typical example, the aluminum strip from which tap lead 26 if formed may be 0.030 inch (30 mils) in thickness. Prior to being spirally wound, the strip-forming lead 26 is preferably tin plated by a commercially available tin plating process such as the Alstan No. 70 process of M. & T. Chemical Company, of which the basic treatment and plating are as follows:

i. The strip is passed through a bath which removes any aluminum oxide coating on the surface of the strip;

2. A thin strike of bronze is deposited on the entire surface of the strip; and

3. the entire surface has a tin plate deposited thereon. Subsequent to the tin plating over the bronze strike, the strip is then preferably spirally wound upon itself and flattened upon itself to form a plurality of spirally wound laminar layers which are attached at one end by welding to a layer or convolution of the aluminum sheet winding 16, as will be described. The multiple layer lead 26 shown in the drawing is illustrated as having six laminar layers. However, the lead 26 may have a different number of layers, as for example, a number of layers in the range of two to 14, depending on such factors as the current carrying requirement for the lead, and the thickness of the individual laminar layers. It is preferred to have the tap lead spirally wound as described and shown. However, the tap lead can also be formed of a plurality of superposed individual laminar strips.

The spiral winding of the aluminum strip to form the multilayer tap lead 26 has the advantage that the lead is mechanically superior to a multilayer lead which is formed of individual conductor strips, and is easier to handle during assembly then a lead formed of individual strips. The loops at the ends of the spirally wound lead hold the respective ends of the lead mechanically assembled. As best seen in the view of FIG. 3, the uppermost or outermost laminar layer 26a of the spirally wound lead 26 is positioned contiguous one surface of a laminar turn or convolution of the winding 16, while the remaining laminar turns collectively indicated at 26b of the lead 26 are positioned contiguous the opposite surface of the same laminar turn or convolution of the sheet winding 16. In other words, in the illustrated embodiment, the convolution or turn of sheet winding 16 to which the tap lead 26 is affixed, is sandwiched" between the outermost laminar layer 26a of the lead 26, on one side and the remaining laminations 26b of the lead 26, on the other side. The tap lead 26 is rigidly secured in electrically conductive relation to the convolution of the aluminum sheet winding 16 by means of a plurality of plug" welds each indicated at 40. In the example shown in the drawing, none plug welds 40 extend across the width of the tap lead, each plug weld 40 extending through the topmost or outermost laminar layer 26a of the lead 26, then through the convolution or turn of sheet winding 16, and then through the plurality of superimposed laminar layers 26b of lead 26. The welds 40 may be of the type shown and described in U.S. Pat. No. 3,102,948 issued to W. M. McCampbell et al. on Sept. 3, 1963 and assigned to the United States of America as represented by the Administrator of the National Aeronautics and Space Administration. The same welding procedure is also shown in NASA Tech Brief No. 64-10309, issued Dec.

1964. In the welding method disclosed by U.S. Pat. No. 3,102,948, McCampbell et al., a welding arc is struck between at least one electrode and the metal workpiece. Filler material is introduced into the arc and the arc is varied as to its length, voltage and current density, in accordance with a predetermined program to gouge out a recess in the weld zone of the workpiece, and then to gradually build up a puddle within the recess so that gases may escape from the puddle and any thermal cracking will be minimized. The puddle solidifies to become a nugget or plug. In the welding method of the Mc- Campbell et al. patent, the welding gun which is used includes means for directing a flow of inert gas or gases to shroud the arc and to purge the space enclosed by the welding nozzle of deleterious gases.

The plug welds which electrically and mechanically join the tap lead- 26 to the turn or convolution of the sheet winding 16 can also be made in accordance with the teaching of U.S. Pat. No. 2,345,037, DeGray, issued Mar. 28, 1944.

Instead of forming the passages through the tap lead and through the turn or convolution of the aluminum sheet winding, by welding techniques as taught by U.S. Pat. No. 3,102,948-McCampbell et al., and No. 2,345,037, DeGray, the holes or passages could instead be made by first punching holes inthe tap lead laminations, and weld material could then be filled into the holes to define plug welds which mechanically and electrically connect the tap lead and the sheet winding. In this embodiment all of the layers of the tap lead are disposed on one side or the other of the convolution of the sheet winding and the sandwiched" arrangement of the winding convolution relative to the tap lead, previously described, is not used.

As best seen in the views of FIGS. 1, 2 and 3, each fixed contact 28 or 28' is connected to a pair of metal studs 45. The two studs 45 pass through the panel board 32 and are tightened in position by nuts 42 each respectively bearing on a washer 44. The tap lead 26 is usually twisted in order that the plane of the multilayer tap lead may be parallel to the plane of the panel or terminal board 32. The end of the tap lead 26 is provided with two passages therethrough which permit the tap lead to be received on the studs 45. A dished spring washer 46 of the type known as a Belleville" washer is positioned on each stud outwardly of the tap lead 26 and an outer nut 48 is positioned on each stud outwardly of the spring washer 46, the nut 48 being tightened to compress the spring washer 46 against the outer surface of the tap lead 26 to hold the tap lead 26 in tightly assembled relation on each stud 45. The spring washer 46, such as the Belleville washer, maintains the tap lead 26 under compression at all times despite differences in temperature coefficients of expansion of the studs 45, which may be made of copper, on the one hand, for example, and of the aluminum tap leads 26, on the other hand.

Tin plating of the multilayer aluminum tap lead on the entire surface thereof and prior to the spiral winding of the tap lead has various advantages. One important advantage is the fact that the addition of the tin plate to the aluminum tap lead eliminates the presence of a high-resistance aluminum oxide layer at the bolted connection of the tap lead 26 to the studs 45, thereby providing a low-contact resistance at the bolted connection, whereas bare aluminum conductors without a tin coating would have a high-resistance aluminum oxide layer on the aluminum at the bolted connection. A further advantage is that the tin plating melts under the welding heat and bonds the adjacent layers of the multiple layer tap lead together to provide a better electrical and mechanical structure.

While tin plating is preferred for economic and other reasons other electrically conductive plating materials such as copper plating, for example, may be used on the aluminum tap lead to prevent the deposit of an undesirable high-resistance aluminum oxide layer. Before applying the copper plating to the aluminum tap lead, the aluminum oxide coating on the tap lead is removed as by passing the tap lead through a bath, as described in connection with the tin'plating operation.

lead laminar layers and thence lengthwise through the tap lead layers to the studs 45.

While the convolution of the aluminum sheetwinding has been shown and described as sandwiched" between the outermost layer of the multiple layer tap lead and the remaining layers of said lead, the positional relationship between the sheet winding and the tap lead may be arranged in other ways. For example,- instead of being sandwiched between the outermost layer of the multiple layer tap lead and the remaining layers of the lead, the convolution of the sheet winding may be sandwiched between any two adjacent layers of the lead. If the multiple layer tap lead 'is spirally wound, it will benecessary to cut an end loop of the lead to permit sandwiching the sheet winding convolution between any two adjacent strip layers which do not include the outermost layer. As previously explained, the sandwiched relation of the winding convolution to the tap lead layers would not be used where the holes for the weld material are prepunched in the conductor lead. In still another alternative, the convolution of the aluminum sheet winding may lie entirely on one side of the multiple layer tap-lead (that is, with all of the layers of the multiple layer tap lead lying on the same side of the convolution of the sheet winding).

Furthermore, as previously mentioned, while it is preferred to spirally wind the tap lead as described and shown, the multiple layer tap lead may instead be made of a plurality of superposed individual strips of aluminum either plated or bare, or other metal of which the tap lead is made, with or without holes punched in the strips prior to the welding operation. As in the case of the spirally wound tap lead, if the plug welds are made by the methods of the McCampbell et al. or De Gray patents previously referred to, the convolution of the sheet winding may be sandwiched between any two adjacent layers of the individual strip tap lead or may be placed in position on either side of the multilayer tap lead. However, if the holes in the tap lead are prepunched, the;convolution of the'sheet winding would not be sandwiched, as previously explained.

If the tap lead is made of aluminum strip, it is preferably tin plated as previously described to provide a low-resistance connection to the contact stud or studs on panel 32.lt is not essential that the tap lead be tin plated at the end, thereof which is attached to the sheet winding. From a practical standpoint, if the aluminum strip tap lead is to be tin plated for .the improved contact at the end thereof which is connected to'the contact stud, it is preferable to tin plate the entire length and area of the tap lead. However, tin plating of the aluminum tap lead strip or other plating of the strip to prevent formation of an oxide coating on the aluminum tap strip lead may be dispensed with entirely, and the low-contact resistance atthe contact stud or terminal end of the tap lead maybe obtained in other ways, such as by means of a transition joint. For example, a copper ferrule may be positioned about and crimped onto the end of the aluminum tap lead which is directed toward the terminal studs and the copper ferrule may then be secured to the stud or studs. Alternatively, a hollow sleevelike electrically conductive joining member may receive the outer end of the aluminum tap lead and also receive a copper tap lead which in turn is secured to the stud or studs. The joining member is in crimped engagement with the two members which it joins. Either of the transition joints just described will provide a low-contact resistance connection to the terminal stud or contact stud without the necessity of tin plating or copper plating the aluminum tap lead. The bare aluminum tap lead may be either spirally wound or made of individual strips of bare aluminum and may be with or without holes prepunched therein, and either the spirally wound tap lead, or

the tap lead formed of individual strips may be arranged relative to the aluminum sheet in the same manners as previously described.

While aluminum, either bare or tin plated, is the preferred material for tap lead, the tap lead material may also be multiple laye r copper strip, either spirally wound or superposed individual strips, and with or without holes punched in the weld region prior to the welding operation.

In using multiple layer copper strip tap leads, it is preferable prior to the welding operation to punch holes in the end of the tap lead which is to be joined to the convolution of the aluminum sheet winding. The end of the tap lead with the holes therein is then positioned in overlying relation to a surface of the aluminum sheet. The holes are then filled with the hot weld material which integrally joins the copper tap lead to the aluminum sheet. 7

An advantage of using copper tap leads is that there is no oxide problem as in the case of aluminum tap leads. This eliminates the need for tin plating or other plating for protection against oxide.

From the foregoing detailed description of the present invention, it has been shown how the objects of the invention have been attained in a preferred manner. However, modifications and equivalents of the disclosed concepts such as readily occur to those skilled in the art are intended to be included within the scope of this'invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A stationary electrical apparatus comprising an electrical winding formed of aluminum sheet material, a multilayer conductive lead extending from said winding, said lead being formed of metal strip material spirally wound on itself, at least one weld connecting said lead to the aluminum sheet material of said electrical winding, a terminal element for said lead carried by said apparatus in spaced relation to said winding, and means connecting said lead to said terminal element.

2. A stationary electrical apparatus comprising an electrical winding formed of aluminum sheet material, a multilayer conductive lead extending from said winding, said lead being formed of metal strip material spirally wound on itself, at least one pluglike spot weld connecting said lead to the aluminum sheet material of said electrical winding, a terminal element for said lead carried by said apparatus in spaced relation to said winding, and means connecting said lead to said terminal element. I

3. A step voltage regulator comprising an electrical winding formed of aluminum sheet material, a multilayer conductive tap lead extending from said winding, said lead being formed of metal strip material spirally wound on itself, at least one pluglike weld connecting said lead to the aluminum sheet materialof said electrical winding, a panel member, a fixed contact mounted on said panel member, electrically conductive stud means mounting said fixed contact to said panel member, and means connecting said lead to said stud means.

4. In combination, an electrical winding formed of aluminum sheet material, a multilayer conductive lead extending from said winding, said lead being formed of metal strip material spirally wound on itself, and at least one pluglike weld connecting said lead to the aluminum sheet material of said electrical winding.

5. A stationary electrical apparatus as defined in claim 2 in which said lead is provided with at least one punched hole therethrough to receive weld material.

6. A stationary electrical apparatus as defined in claim 2 in which said winding includes a winding convolution which is attached to said lead on one side of said lead, with all of the strip layers of said lead lying on the same side of said convolution.

7. A stationary electrical apparatus as defined in claim 2 in which said winding includes a winding convolution which is sandwiched between any two adjacent layers of the multilayer lead.

8. A stationary electrical apparatus as defined in claim 2 in which said lead is a strip of aluminum spirally wound on itself to form a multilayer lead.

9. A stationary electrical apparatus as defined in claim 2 in which said lead is formed of aluminum and is metal plated for at least the portion thereof connected to said terminal element to prevent the formation of an aluminum oxide layer on said portion so coated.

10. A stationary electrical apparatus as defined in claim 2 in which said lead is formed of aluminum and is tin plated for at least the portion thereof connected to said terminal element.

11. A stationary electrical apparatus as defined in claim 2 in which said lead is formed of aluminum and is tin plated on substantially the entire surface area thereof.

12. A stationary electrical apparatus as defined in claim 2 in which said lead is formed of aluminum and is copper plated for at least the portion thereof connected to said terminal element.

13. A stationary electrical apparatus as defined in claim 2 in which said lead is a strip of copper spirally wound on itself to form a multilayer lead.

14. A step voltage regulator comprising an electrical winding formed of aluminum sheet material, a multilayer conductive tap lead extending from said winding, said lead being fonned of metal strip material spirally wound on itself, at least one weld connecting said lead to the aluminum sheet material of said electrical winding, a panel member, a fixed contact mounted on said panel member, electrically conductive stud means mounting said fixed contact to said panel member, and means connecting said lead to said stud means.

15. A step voltage regulator as defined in claim 3 in which said lead is provided with at least one punched hole therethrough to receive weld material.

16. A step voltage regulator as defined in claim 3 in which said winding includes a winding convolution which is attached to said lead on one side of said lead, with all of the strip layers of said lead lying on the same side of said convolution.

17. A step voltage regulator as defined in claim 3 in which said winding includes a winding convolution which is sandwiched between any two adjacent layers of the multilayer lead.

18. A step voltage regulator as defined in claim 3 in which said lead is a strip of aluminum spirally wound on itself to form a multilayer lead.

19. A step voltage regulator as defined in claim 3 in which said lead is formed of aluminum and is tin plated for at least the portion thereof connected to said stud means.

20. A step voltage regulator as defined in claim 3 in which said lead is formed of aluminum and is tin plated on substantially the entire surface area thereof.

21. A step voltage regulator as defined in claim 3 in which said lead is formed of aluminum and is copper plated for at least the portion thereof connected to said stud means.

22. A step voltage regulator as defined in claim 3 in which said lead is a strip of copper spirally wound on itself to form a multilayer lead.

23. A step voltage regulator as defined in claim 3 in which said lead is made of copper and is provided with at least one punched hole therethrough to receive weld material.

* i I i 

1. A stationary electrical apparatus comprising an electrical winding formed of aluminum sheet material, a multilayer conductive lead extending from said winding, said lead being formed of metal strip material spirally wound on itself, at least one weld connecting said lead to the aluminum sheet material of said electrical winding, a terminal element for said lead carried by said apparatus in spaced relation to said winding, and means connecting said lead to said terminal element.
 2. A stationary electrical apparatus comprising an electrical winding formed of aluminum sheet material, a multilayer conductive lead extending from said winding, said lead being formed of metal strip material spirally wound on itself, at least one pluglike spot weld connecting said lead to the aluminum sheet material of said electrical winding, a terminal element for said lead carried by said apparatus in spaced relation to said winding, and means connecting said lead to said terminal element.
 3. A step voltage regulator comprising an electrical winding formed of aluminum sheet material, a multilayer conductive tap lead extending from said winding, said lead being formed of metal strip material spirally wound on itself, at least one pluglike weld connecting said lead to the aluminum sheet material of said electrical winding, a panel member, a fixed contact mounted on said panel member, electrically conductive stud means mounting said fixed contact to said panel member, and means connecting said lead to said stud means.
 4. In combination, an electrical winding formed of aluminum sheet material, a multilayer conductive lead extending from said winding, said lead being formed of metal strip material spirally wound on itself, and at least one pluglike weld connecting said lead to the aluminum sheet material of said electrical winding.
 5. A stationary electrical apparatus as defined in claim 2 in which said lead is provided with at least one punched hole therethrough to receive weld material.
 6. A stationary electrical apparatus as defined in claim 2 in which said winding includes a winding convolution which is attached to said lead on one side of said lead, with all of the strip layers of said lead lying on the same side of said convolution.
 7. A stationary electrical apparatus as defined in claim 2 in which said winding includes a winding convolution which is sandwiched between any two adjacent layers of the multilayer lead.
 8. A stationary electrical apparatus as defined in claim 2 in which said lead is a strip of aluminum spirally wound on itself to form a multilayer lead.
 9. A stationary electrical apparatus as defined in claim 2 in which said lead is formed of aluminum and is metal plated for at least the portion thereof connected to said terminal element to prevent the formation of an aluminum oxide layer on said portion so coated.
 10. A stationary electrical apparatus as defined in claim 2 in which said lead is formed of aluminum and is tin plated for at least the portion thereof connected to said terminal element.
 11. A stationary electrical apparatus as defined in claim 2 in which said lead is formed of aluminum and is tin plated on substantially the entire surface area thereof.
 12. A stationary electrical apparatus as defined in claim 2 in which said lead is formed of aluminum and is copper plated for at least the portion thereof connected to said terminal element.
 13. A stationary electrical apparatus as defined in claim 2 in which said lead is a strip of copper spirally wound on itself to form a multilayer lead.
 14. A step voltage regulator comprising an electrical winding formed of aluminum sheet material, a multilayer conductive tap lead extending from said winding, said lead being formed of metal strip material spirally wound on itself, at least one weld connecting said lead to the aluminum sheet material of said electrical winding, a panel member, a fixed contact mounted on said panel membeR, electrically conductive stud means mounting said fixed contact to said panel member, and means connecting said lead to said stud means.
 15. A step voltage regulator as defined in claim 3 in which said lead is provided with at least one punched hole therethrough to receive weld material.
 16. A step voltage regulator as defined in claim 3 in which said winding includes a winding convolution which is attached to said lead on one side of said lead, with all of the strip layers of said lead lying on the same side of said convolution.
 17. A step voltage regulator as defined in claim 3 in which said winding includes a winding convolution which is sandwiched between any two adjacent layers of the multilayer lead.
 18. A step voltage regulator as defined in claim 3 in which said lead is a strip of aluminum spirally wound on itself to form a multilayer lead.
 19. A step voltage regulator as defined in claim 3 in which said lead is formed of aluminum and is tin plated for at least the portion thereof connected to said stud means.
 20. A step voltage regulator as defined in claim 3 in which said lead is formed of aluminum and is tin plated on substantially the entire surface area thereof.
 21. A step voltage regulator as defined in claim 3 in which said lead is formed of aluminum and is copper plated for at least the portion thereof connected to said stud means.
 22. A step voltage regulator as defined in claim 3 in which said lead is a strip of copper spirally wound on itself to form a multilayer lead.
 23. A step voltage regulator as defined in claim 3 in which said lead is made of copper and is provided with at least one punched hole therethrough to receive weld material. 